基于脉冲激光离散划痕技术的涂层表面动态应变实验研究

Experimental Study of Dynamic Strain on Coating Surface Based on Pulse Laser Discrete Scratching Technique

脉冲激光离散划痕过程中,激光冲击波动态加载及界面破坏在瞬间完成。其所包含的脱粘、裂纹扩展、翘曲、断裂和剥落往往无法分辨。为了准确判断涂层失效的临界点,提出一种利用应变诊析膜基系统失效临界点的方法。利用双面胶作为粘结剂,2024铝合金为基体,304不锈钢箔为涂层构建膜基系统理论模型,采用PVDF贴片传感器技术研究了脉冲激光作用下不同理论模型涂层表面的动态应变。结果表明:脉冲激光作用下,涂层表面的动态应变不断往复变化,最终趋于平衡,整个过程在微秒量级的时间内完成。同时,涂层表面的动态响应与膜基系统界面结合状况有关,膜基系统结合完好时,涂层表面的动态响应时间长,得到的最终应变量小。膜基系统全完脱粘时,涂层表面的动态响应时间短,最终应变量大,膜基系统刚开始脱粘的试样介于两者之间。

During the pulse laser discrete scratching process, laser shock wave dynamic loading and interface failure are completed instantly. It contains debond, crack extension, warping, fracture and peeling which are often unable to distinguish. In order to accurately determine the critical point of the coating failure and propose a strain method to dialysis film-substrate system failure, this paper researched dynamic strain on coating surface of different theoretical models under pulse laser processing using PVDF patch sensors. The theoretical models are composed by double-sided adhesive binder, 2024 aluminum alloy substrate and 304 stainless steel foil film. The results indicate that under laser shock processing the dynamic strain on the coating surface fluctuates constantly, and then tends to steady. The whole process is finished in microseconds. The dynamic response of the coating surface is associated with interface bonding status of film-substrate system. When the film-substrate system combined well, the dynamic response＇s duration is long and the final strain value is small. When the film-substrate system debonded completely, the duration of the dynamic response is short and the obtained strain value is big. If the film- substrate system just began to debond, the situation will between this two pole conditions.